Upper limb performance and the structuring of joint movement in teenagers with cerebral palsy: the reciprocal role of task demands and action capabilities

Precision aiming performance with the paretic upper limb is associated with center of pressure patterns in individuals with chronic stroke

BACKGROUND

Individuals with stroke commonly demonstrate upper-limb sensorimotor impairments. Upper-limb tasks occur against a background level of postural control and thus require a flexible postural control system to facilitate performance. Anterior precision aiming tasks, for example, benefit from lower medial-lateral (ML) center of pressure (COP) fluctuations (where increased fluctuations erode performance) relative to anterior-posterior (AP) fluctuations (where increased fluctuations do not strongly influence performance). After stroke, individuals may compensate for upper-limb impairments by increasing trunk movement which increases overall COP fluctuations and thus may make it more difficult to modulate COP in a task-sensitive manner.

RESEARCH QUESTION

Do upper-limb task demands modulate COP movement patterns after stroke?

METHODS

In this cross-sectional study, adults with chronic stroke (n = 23) and unilateral upper-limb impairments were immersed in a virtual environment displaying an anterior target. Participants aimed to maintain the position of a virtual laser pointer (via handheld controller) in the target with each hand. COP was concurrently recorded. Mixed effects models and correlations were used to detect differences in COP patterns between limbs and movement planes and evaluate associations between task performance and COP patterns, respectively.

RESULTS

Participants showed greater COP standard deviation and regularity in the AP compared to the ML direction. The magnitude of difference between AP and ML COP metrics was greater using the nonparetic limb. Task performance was moderately and positively associated with task-sensitive COP patterns (i.e., higher AP:ML ratios of COP metrics) using the paretic upper limb. Participants consistently demonstrated high levels of task performance and task-sensitive COP movement patterns using the nonparetic limb.

SIGNIFICANCE

Impairments in postural control after stroke may be related to the upper limb used. It is important to recognize the role of directional COP variability and regularity in the context of a task goal after stroke.

Rhythm and Reaching: The Influence of Rhythmic Auditory Cueing in a Goal-Directed Reaching Task With Adults Diagnosed With Cerebral Palsy

Improvements in functional reaching directly support improvements in independence. The addition of auditory inputs (e.g., music, rhythmic counting) may improve goal-directed reaching for individuals with cerebral palsy (CP). To effectively integrate auditory stimuli into adapted teaching and rehabilitation protocols, it is necessary to understand how auditory stimuli may enhance limb control. This study considered the influence of auditory stimuli during the planning or execution phases of goal-directed reaches. Adults (with CP = 10, without CP = 10) reached from a home switch to two targets. Three conditions were presented-no sound, sound before, and sound during-and three-dimensional movement trajectories were recorded. Reaction times were shorter for both groups in the sound before condition, while the group with CP also reached peak velocity relatively earlier in the sound before condition. The group with CP executed more consistent movements in both sound conditions. Sound presented before movement initiation improved both the planning and execution of reaching movements for adults with CP.

A novel single-leg squat test with speed and accuracy requirements: Reliability and validity in anterior cruciate ligament reconstructed individuals

BACKGROUND

Some traditional single-leg squat tests focused on number of repetitions may not demand precise control of lower limb dynamic alignment, especially in the frontal and transverse planes. The primary objective of this study was to evaluate test-retest reliability and construct validity of a novel single-leg squat test - the 'precision-squat test' (PST) - designed to assess performance under varying task demands that can impact the execution of lower limb movements. A secondary objective was to investigate whether musculoskeletal factors predict performance in the PST in healthy individuals.

METHODS

Thirty healthy participants were assessed to verify test-retest reliability. To verify the test's construct validity, we compared the performance of 21 anterior cruciate ligament reconstructed (ACLR) individuals and 21 matched controls. Finally, 36 healthy individuals were assessed to verify the musculoskeletal factors related to PST performance. All participants performed the PST: they executed single-leg squats while moving a laser pointer (attached to the thigh) between two targets. We varied target size and distance between targets to manipulate the task difficulty.

RESULTS

Reliability of the PST was excellent at all demand levels (intraclass correlation coefficient (ICC)_(3,2) > 0.93). Squat time increased under test conditions involving higher task difficulty (P < 0.001) and in ACLR individuals compared with age-matched controls (P < 0.05). Regression analyses revealed that reduced knee extensors and hip external rotators torques are related to increased squat time (P < 0.05).

CONCLUSIONS

PST is a valid and reliable tool to assess performance of healthy and ACLR individuals. In addition, hip and knee strength are associated with performance during the test.

Evaluation of speed-accuracy trade-off in a computer task in individuals with cerebral palsy: a cross-sectional study

BACKGROUND

Individuals with Cerebral Palsy (CP) present with sensorimotor dysfunction which make the control and execution of movements difficult. This study aimed to verify the speed-accuracy trade-off in individuals with CP.

METHODS

Forty eight individuals with CP and 48 with typical development (TD) were evaluated (32 females and 64 males with a mean age of 15.02 ± 6.37 years: minimum 7 and maximum 30 years). Participants performed the "Fitts' Reciprocal Aiming Task v.1.0 (Horizontal)" on a computer with different sizes and distance targets, composed by progressive indices of difficulty (IDs): ID2, ID4a and ID4b.

RESULTS

There were no statistical differences between the groups in relation to the slope of the curve (b1) and dispersion of the movement time (r²). However, the intercept (b0) values presented significant differences (F(1.95) = 11.3; p = .001]), with greater movement time in the CP group compared to the TD group. It means that for individuals with CP, regardless of index difficulty, found the task more difficult than for TD participants. Considering CP and TD groups, speed-accuracy trade-off was found when using different indices of difficulty (ID2 and ID4). However, when the same index of difficulty was used with a larger target and longer distance (ID4a) or with a narrow target and shorter distance (ID4b), only individuals with CP had more difficulty performing the tasks involving smaller targets. Marginally significant inverse correlations were identified between the values of b1 and age (r = -0.119, p = .052) and between r² and Gross Motor Function Classification System (r = -0.280, p = .054), which did not occur with the Manual Ability Classification System.

CONCLUSION

We conclude that the individuals with CP presented greater difficulty when the target was smaller and demanded more accuracy, and less difficulty when the task demanded speed. It is suggested that treatments should target tasks with accuracy demands, that could help in daily life tasks, since it is an element that is generally not considered by professionals during therapy.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT03002285 , retrospectively registered on 20 Dec 2016.